1. Field of the Invention
This invention relates to a cable and its method of manufacture and, more particularly, to a folded cable and its method of manufacture.
2. Description of the Related Art
Cables generally are used as pathways for transmitting signals to and from equipment. For example, an electrical cable or an optical fiber cable may interconnect two computers so that data may be shared between the computers. Signals corresponding to the data to be shared are transmitted via conductors (e.g., electrical conductors or fiber optic conductors) within the cable. Conductors within cables may also be used as pathways to supply power to equipment.
Historically, such cables have been made of individual conductors arranged in a generally round bundle and sheathed by shielding and/or insulating jackets. Ends of the conductors may be soldered, crimped, or otherwise mechanically attached to connectors that mate with connectors on the equipment to be interconnected. Such attachments may, over time, loosen due to cable flexure or to vibrations imposed on the cable as a result of the environment in which the cables are used.
Further, such cables tend to be large in diameter if they contain large numbers of conductors, which may impair the flexibility of the cable. These types of cables may also be heavy, which may be less desirable in applications such as aircraft, missiles, or the like where weight is a prime design factor.
Flexible printed wiring cables may overcome some of the flexibility and weight issues found in round conventional cables. However, such cables are generally limited in the number of conductors that they may contain. Further, it may be difficult to shield this type of cable from aggressive electromagnetic interference (“EMI”).
Flexible printed wiring cables have been made using photolithography and etching processes, similar to those used in the printed circuit board industry. For example, such cables may be made from panels comprising a layer of photosensitive material covering a layer of copper (or other conductor) plated onto a dielectric substrate. Generally, an image of the desired conductor pattern may be transferred onto the photosensitive layer. The portion of the photosensitive material not covering the conductor pattern is washed away, and the panel is acid etched to remove the uncovered copper. The remaining photosensitive material may then be washed away, leaving the conductor pattern exposed. A dielectric layer is generally applied over the conductor pattern to electrically insulate the conductors.
Lengths for such cables have traditionally been limited to the size of the panel being used as raw material in the process. Single substrate cables, having conductors either on one or both sides of the substrate, have been made in serpentine patterns and then folded sharply along fold lines to form cables that can span longer distances. Overlapping areas in the cable may be adhesively bonded together to retain the cable in a folded configuration. Such cables have been generally limited to a single substrate, as described above, due to the sharpness of the fold. Thus, these cables are also limited in the number of conductors that they may include.
Accordingly, a need exists for a lightweight, flexible cable that may include a great number of conductors and that may be manufactured at a reasonable cost. The present invention is directed to overcoming, or at least reducing, the effects of one or more of the problems set forth above.